Index: /trunk/src/org/openstreetmap/josm/data/validation/tests/MapCSSTagChecker.java
===================================================================
--- /trunk/src/org/openstreetmap/josm/data/validation/tests/MapCSSTagChecker.java	(revision 6582)
+++ /trunk/src/org/openstreetmap/josm/data/validation/tests/MapCSSTagChecker.java	(revision 6583)
@@ -235,5 +235,6 @@
             final StringBuffer sb = new StringBuffer();
             while (m.find()) {
-                m.appendReplacement(sb, determineArgument((Selector.GeneralSelector) matchingSelector, Integer.parseInt(m.group(1)), m.group(2)));
+                final String argument = determineArgument((Selector.GeneralSelector) matchingSelector, Integer.parseInt(m.group(1)), m.group(2));
+                m.appendReplacement(sb, String.valueOf(argument));
             }
             m.appendTail(sb);